Teaching Case

A 78-year-old lady was diagnosed with metastatic renal cell carcinoma, including a hypervascular lesion in the left femoral diaphysis. The decision was taken to perform a preventive left femur fixation. However, a preoperative transarterial embolisation was needed to reduce the risk of intra-operative bleeding.

Under local anaesthetic, ultrasound-guided retrograde right common femoral artery 5F Destination sheath access for up and over approach. Aortic bifurcation crossed with 5F Vector 4 catheter and 0.35 Advantage wire. Angiography demonstrated multiple pathological branches from the left profunda femoris and superficial femoral arteries, supplying the hypervascular femoral lesion (Figures 1 and 2).

Selective and super-selective cannulation with a 2.8F Progreat catheter of the left profunda femoral artery and its branches, followed by target embolisation with Contour 500-710 microns particles achieving a very good result (Figure 3).

Then, selective and super-selective cannulation with a 2.8F Progreat catheter of the left SFA branches supplying the lesion. Two branches were embolised using 2 mm protective micro-coils to avoid nontarget embolisation with particles (Figure 4), and one genicular branch was embolised with Contour 500-710 microns particles (Figure 5).

Although unsuccessful attempts to cannulate an SFA branch supplying the lesion, the final angiographic result was good (Figure 6). Subsequently, the patient had the intramedullary fixation with no significant complication.

Metastasis is the most common malignant lesion of the bone and is associated with significant morbidity. Symptoms of bone metastasis, such as pain or impending fracture, are often treated with medical therapy or radiotherapy, with variable results. In the past few years, interventional radiology (IR) has taken up an increasing role in managing bone metastasis. IR can be used as a curative treatment in selected patients or as a palliative strategy, often as pain relief. IR offers several advantages, such as no need for interruption of systemic tumour therapy, reduced morbidity and in-hospital stay, and fast recovery. The decision to perform an IR procedure in a patient with osseous metastasis must be taken upon consensus by a tumour board meeting.

The most common IR procedures of bone metastasis are osteoplasty, osteosynthesis, thermal ablation, and embolisation. Trans-arterial embolisation (TAE) is the interventional technique in which hypervascular bone metastases are selectively de-vascularised with the preservation of all non-target vessels. Possible indications for reducing tumour vascularity with TAE are to minimise blood loss during surgery, like in this case, relieve pain, and reduce the risk of spontaneous bleeding [1]. And limit the heat sink effect from surrounding vessels during thermal ablation. In an RCT by Clausen et al, preoperative TAE led to significant reduction in operating time [2].

The interventional technique depends on the indication, vessels, and regional anatomy. In this case, we decided to access from the contralateral common femoral artery because these lesions usually have apparent and proximal feeding arteries, and accessing from the contralateral approach would help us assess those.

Embolic agents used can be temporary or permanent and liquid or solid. Permanent agents are mostly used in a preoperative or a palliative setting. Although we used PVA, Basile A et al have found that calibrated 300–500-micron particles are preferred embolic agents because they are more predictable and less likely to clump and occlude the microcatheter. However, either PVA or clear acrylic copolymer can be used, and no clinical advantage has been identified with using one over the other [3].

Caution should be taken when 100-300 micron particles are used because the osseous arteries are not end arteries, and there is a risk of trans-tumoural non-target embolisation. Therefore, particles of less than 100 micros should be avoided. Also, we used the micro-coils in this case as we couldn't safely fix the microcatheter in two SFA branches, and to avoid non-target embolisation.

In cases where there is a high risk of non-target embolisation associated with a hypervascular lesion, it is crucial to use an anti-reflux microcatheter. These specialised catheters employ advanced technologies that ensure precise and safe delivery of embolic material to the intended tumour, preventing any backflow and enhancing the effectiveness of the procedure.

Another option is to use a balloon-occlusion microcatheter for pressure-directed embolisation. This technique is based on a well-established principle of fluid dynamics, where liquids naturally flow from areas of high pressure to low pressure. By occluding a supply artery with a balloon, hemodynamic changes occur that increase the delivery of the embolic agent specifically into the targeted tumours, facilitating greater penetration of the embolic material into the tumour's microvasculature. Additionally, this technique provides an anti-reflux mechanism [4].

Liquid embolic materials like glue have been used but are limited to high-volume centres. The gel foam causes proximal occlusion and is less precise. Also, it can cause blocking of the microcatheter and may lead to reflux and non-target embolisation if unblocking the microcatheter is attempted. Therefore, using gel foam is discouraged.

Furthermore, the literature suggests residual tumoral blush of up to 30% is acceptable, which would be helpful to decide the end-point in cases with multiple and complex arterial supply [5].

In conclusion, embolisation is underutilised in treating hypervascular bone metastases despite substantial evidence it simplifies surgery and reduces the risk of intraoperative complications. In addition, it's a powerful tool for palliation and, with caution, a very safe procedure.

All patient data have been completely anonymised throughout the entire manuscript and related files.